Hi Lee,
If a greyhound cramps in a specific group of muscles after running it generally indicates one of two problems.
These are; muscle damage in one or more of the muscle group that is cramping, or an impaired nerve supply to the muscles that cramp.
The most common reason still is muscle damage which is likely to include scar tissue and some damage in the blood vessels to that muscle tissue, thereby reducing blood flow to the area.
While there is not a lot that can be done when there is damage to the blood supply, very light massage and warming the muscles prior to running will help. Also firm massage plus the application of a warming liniment after running to the same area, whether it has cramped or not, will also be of great long term benefit.
If part of the cause is impaired nerve supply to that group of muscles, you should be able to see that the muscles on that shoulder are fractionally smaller and more visibly flatter than the same muscles on the other shoulder.
If that is the case then the most likely cause will be muscle spasms or muscle damage causing muscles spasms to the lower part of the neck on the side of the body where the shoulder is affected. This causes alignment problems to the lower two neck segments and where the neck bones connect to the rest of the spine.
The main major nerve affected by this is the radial nerve of the shoulder, and if this nerve is affected It also often causes pain along the spine of the scapula.
To relieve problems in this area firm deep massage to the lower part of neck and down into the top of the saddle muscles is best.
Followed by gentle stretching of the area done by first standing astride the greyhound, sliding your arm from behind the upper part of the front leg in between both front legs, and then by curling your hand around the front of the other leg as high as possible, you lift the front of the greyhound up off the ground just a 100 mm.
When lifted up in that manner the neck of the greyhound will naturally fall to the side where you have your fingers hooked around the lower shoulder, and then with your other arm laid across the neck slight pressure will then allow you to gently stretch the neck further down and around to that side. Then simply swap arms and repeat the procedure on the other side of the body.
In rare instances it is possible for nerve impairment to be caused by damage, and or muscle spasms in the atlas where the head connects to the neck. Damage done to the greyhound by running into a gate, fence, or crashing into the starting box lid.
However unless a considerable amount of experience is available in spinal manipulation the only thing that can be safely done to that area is gentle massage with a warming liniment to the hollows each side of the neck where the head joins the spine. Keeping in mind that if nerve impairment is caused by problems around the atlas then in most instances both sides of the front of the greyhound would be affected.
Cheers,
Tom